The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS) is an architectural framework for delivering IP multimedia services. IMS uses Internet Engineering Task Force (IETF) protocols for transactions and the managements thereof, predominantly the Session Initiation Protocol (SIP). In IMS architectures, a Serving Call Session Control Function (S-CSCF) server and an Application Server, which in a case of telephony services, is also referred to as Telephony Application Server (TAS), are critical functions in controlling packet switched connectivity for a service(s) session, e.g., a voice call session.